Airbag modules consist of casings in which a folded cushion is fixed, which cushion quickly inflates by means of a gas produced by a generator when specific sensing devices detect a vehicle collision. The cushion thus deploys in front of the driver or a passenger, depending on its location, and prevents their bodies from hitting against any part of the vehicle.
To prevent the cushion from being too stiff when it comes into contact with the driver or passenger, acting as if it were a ball and making the rebound effect cause an excessive impact in the person for whom it deploys, they have been provided with a ventilation hole used to reduce the internal pressure of the cushion and, consequently, the possibility of causing injuries when actuated.
At the same time, several means for sealing the gas discharge hole have been used to achieve better control of the internal pressure of the cushion than the one provided only by the variation of the hole size.
Using a sealing patch achieves that the gas does not come out immediately through the discharge hole but rather when the patch breaks.
The art has proposed different types of patches with different means for controlling their breaking according, to a greater or lesser extent, to a specific resistance to the gas pressure inside the cushion. The presence of the necessary gas pressure for the cushion to carry out its protective function is thus made compatible with the guarantee that the gas pressure will not achieve an excessive value, with risks for the people for whom the cushion deploys.
Fabric patches such as those described in patent documents U.S. Pat. No. 3,879,057, U.S. Pat. No. 4,097,065 and U.S. Pat. No. 5,018,761 have been proposed, said patches not being successful due to the lack of breaking pressure uniformity as a result of their nature.
Nor have plastic patches such as those proposed in patent document U.S. Pat. No. 3,573,885 been successful because of the difficulty in controlling their breaking pressure due to the variability of mechanical characteristics of plastic at different temperatures.
In this sense, patches made of an elastic material such as silicone are currently considered the most suitable because of the good stability of the material in temperature changes. Patches with different shapes and thicknesses are used to control the breaking pressure for the purpose of optimizing their conditions for holding back the occupant of the vehicle they are intended for. A good example to that respect is the one described in patent application EP 1022198.
The cushions to which said patches are fixed must be coated with silicone to facilitate fixing the patch to the cushion by means of a gluing process, which involves a drawback because this coating increases the cost of the cushion and reduces its packaging capacity.
The present invention aims to solve this drawback.